<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>花样转场</title>
  <style>
    body {
      margin: 0;
      overflow: hidden
    }
  </style>
</head>

<body>
  <canvas id="canvas"></canvas>
  <script id="vertexShader" type="x-shader/x-vertex">
    attribute vec4 a_Position;
    attribute vec2 a_Pin;
    varying vec2 v_Pin;
    void main(){
      gl_Position = a_Position;
      v_Pin=a_Pin;
    }
  </script>
  <script id="fragmentShader" type="x-shader/x-fragment">
    precision mediump float;
    uniform sampler2D u_Sampler;
    uniform sampler2D u_Pattern;
    uniform sampler2D u_Gradient;
    uniform float u_Ratio;
    varying vec2 v_Pin;
    void main(){
      vec4 o=texture2D(u_Sampler,v_Pin);
      vec4 p=texture2D(u_Pattern,v_Pin);
      vec4 g=texture2D(u_Gradient,v_Pin);
      float f=clamp((g.r + u_Ratio), 0.0, 1.0);
      gl_FragColor=mix(o,p,f);
    }
  </script>
  <script type="module">
    import Track from "../jsm/Track.js";
    import { imgPromise, initShaders, } from '../jsm/Utils.js';
    import Poly from './jsm/Poly.js';

    const canvas = document.getElementById('canvas');
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    const gl = canvas.getContext('webgl');

    const vsSource = document.getElementById('vertexShader').innerText;
    const fsSource = document.getElementById('fragmentShader').innerText;
    initShaders(gl, vsSource, fsSource);
    gl.clearColor(0.0, 0.0, 0.0, 1.0);

    //数据源
    const source = new Float32Array([
      -0.4, 0.8, 0, 1,
      -0.4, -0.8, 0, 0,
      0.4, 0.8, 1, 1,
      0.4, -0.8, 1, 0,
    ]);

    let n = 0
    let len = 5
    const obj = { ratio: 0 }
    let track = null

    const rect = new Poly({
      gl,
      source,
      type: 'TRIANGLE_STRIP',
      uniforms: {
        u_Ratio: {
          type: 'uniform1f',
          value: obj.ratio
        }
      },
      attributes: {
        a_Position: {
          size: 2,
          index: 0
        },
        a_Pin: {
          size: 2,
          index: 2
        },
      }
    })



    loadImg()

    function loadImg() {
      n++;
      const i1 = n % len
      const i2 = (n + 1) % len
      const i3 = Math.round(Math.random() * 4)

      const originImg = new Image()
      originImg.src = `./images/pattern${i1}.jpg`

      const pattern = new Image()
      pattern.src = `./images/pattern${i2}.jpg`

      const gradient = new Image()
      gradient.src = `./images/mask${i3}.jpg`

      Promise.all([
        imgPromise(originImg),
        imgPromise(pattern),
        imgPromise(gradient),
      ]).then(() => {
        changeImg(originImg, pattern, gradient)
        ani()
      })
    }

    function changeImg(...imgs) {
      obj.ratio = 0

      rect.maps = {
        u_Sampler: { image: imgs[0] },
        u_Pattern: { image: imgs[1] },
        u_Gradient: { image: imgs[2] },
      }
      rect.updateMaps()
      track = new Track(obj);
      track.start = new Date();
      track.timeLen = 2000;
      track.onEnd = loadImg
      track.keyMap = new Map([
        [
          "ratio",
          [
            [0, 0],
            [1000, 1]
          ],
        ],
      ]);
    }


    /* 动画 */
    function ani() {
      track.update(new Date())
      rect.uniforms.u_Ratio.value = obj.ratio;
      rect.updateUniform()
      render()
      requestAnimationFrame(ani)
    }

    //渲染
    function render() {
      gl.clear(gl.COLOR_BUFFER_BIT);
      rect.draw()
    }
  </script>
</body>

</html>